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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Case study investigation of meso-synoptic scale effects on the total ozone column

Murphey, Bill B. 08 1900 (has links)
No description available.

A comparison of stratospheric aerosol and gas experiment I (SAGE I) and umkehr ozone profiles including a search for umkehr aerosol effects

Newchurch, Michael Joseph 05 1900 (has links)
No description available.

A study of tropospheric photochemistry in the subtropical/tropical North and South Atlantic

Chen, Gao 05 1900 (has links)
No description available.

The interpretation of SAGE II ozone measurements in the lower mesosphere

Chu, Ding-Chong Allen 05 1900 (has links)
No description available.

Latitudinal and vertical relationships between tropospheric ozone and water vapor as measured in Project Gametag

Routhier, Francis Xavier 08 1900 (has links)
No description available.

The absorption spectrum of ozone in solution

Robinson, George Wilse 08 1900 (has links)
No description available.

Analysis of PSC Formation using Parcel Temperature Histories

Dennison, Fraser January 2013 (has links)
Polar Stratospheric Clouds (PSCs) are composed of H₂SO₄/HNO₃/H₂O aerosols called supercooled ternary solution (STS), solid nitric acid trihydrate (NAT) particles and ice particles. These clouds require the low temperatures found in the polar regions of the lower stratosphere to occur. PSCs are important due to the critical role they play in the destruction of ozone over the poles. The role of PSCs in ozone destruction has been understood since the 1980’s however the mechanisms involved in PSC formation, particularly NAT formation, is still not well understood. Typically formation of PSCs in climate models is handled by using a temperature threshold as a proxy. A commonly used threshold is the equilibrium temperature for the existence of NAT, TNAT ; however when the area with temperatures below TNAT are compared with observations of PSC it is found that this measure significantly over-estimates the abundance of PSC. This research uses back trajectories stemming from the site of PSC observations to investigate the effect that the temperature history has on PSC formation. The trajectories are calculated using a simple Lagrangian model on an isentropic surface. The observational PSC data is obtained from the CALIOP (Cloud Aerosol Lidar with Orthogonal Polarization) instrument, which is from the CALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) mission launched in 2006. The CALIOP data used in this research is taken from the June to September period from the years 2007-10 and for latitudes between -55° and -82°S, and totals in excess of 7 million individual measurement profiles, a four day back trajectory is calculated for each observation along the 450 K isentropic level. Temperature and wind data is from the MERRA (Modern Era Retrospective-analysis for Research and Applications) reanalysis and H₂O and HNO₃ concentrations (required for calculating equilibrium temperatures) are from Earth Observing System (EOS) Aura Microwave Limb Sounder (MLS) version 3.3. It was found that different PSC types had different characteristics in their temperature histories. The mean temperature history associated with ice observations cooled by around 3 K over the previous 24 hours to slightly below the water ice frost point at the time of observation. However, in trajectories associated with the presence of NAT the temperature has on average stayed 4-5 K below TNAT for the entire four days of the trajectory. Based on these findings and theories of PSC formation, a system for predicting PSC occurrence based on the temperature histories is proposed. This system provides a better approximation for the total extent of PSC occurrence than the TNAT threshold. The average area covered by PSC on the 450 K level over the period examined as observed by CALIOP was 7.6 million km² while the area predicted by the temperature histories was 8.6 million km² as compared to 20.4 million km² with temperatures below TNAT. The average geographical coverage of the different PSC types is reasonably well replicated by the temperature history classification; however, the ability to discriminate between different PSC types based on individual temperature histories is somewhat limited.

Low temperature oxidation of VOCs in air by catalytic ozonation

2014 August 1900 (has links)
Alumina supported manganese oxides were used in the gas phase oxidation of toluene by ozone. Catalyst activity and characterization, the promotional effect of noble metals (Pt and Pd) on the activity of manganese oxides, and the kinetics and mechanism of the reaction were investigated in this PhD thesis. It was shown that MnO2 and Mn2O3 were the active sites of the catalyst capable of oxidizing toluene to CO and CO2 below 100 oC. Catalysts were deactivated at room temperature due to the accumulation of carbonaceous species on their surface. At least 65 oC was required for the stable operation of the catalysts. X-ray absorption spectroscopy was used to study the structure and electronic properties of the mono metallic and bimetallic catalysts. It was found that the catalysts with higher Mn loading resulted in higher oxidation states of Mn which were less favorable for the oxidation of toluene. The addition of Pt to the Mn containing catalyst increased the reaction rate by transferring electrons from Pt to Mn. On the other hand, no promotional effect was observed by the addition of Pd to Mn. The Oxidation state of Mn atoms was one of the most important parameters, controlling the rate of toluene oxidation. Lower oxidation states of Mn were able to easily transfer electrons to ozone, accelerating the rate of toluene oxidation. A reaction mechanism was proposed for the catalytic oxidation of toluene over manganese oxides. In this mechanism, the oxidation of toluene was carried out by the abstraction of hydrogen atoms followed by the oxidation of toluene carbon skeleton. A rate equation was derived based on this mechanism, determining the reaction orders of -1 and 2 for toluene and ozone, respectively. It was concluded that catalytic ozonation is an effective method for the low temperature oxidation of volatile organic compounds (VOCs) in air. The significance of this method is related to energy saving in air purifying systems by reducing the required temperature to oxidize VOCs. Catalytic ozonation can be used in indoor and outdoor applications for removal of VOCs from enclosed environments or polluted industrial streams.

The effect of exposure to ozone on energy metabolism in heart, liver, and skeletal muscle tissues

Mcallister, Richard Murray January 1982 (has links)
Energy Metabolism in Heart, Previous studies have demonstrated that acute or chronic exposureto ozone results in (1) alterations in the glutathione peroxidase system, and (2) the functional activity of sulfhydryls and sulfhydryl-contain+nq enzymes in lung tissue and erythrocytes. As a result, both structural damage and changes in metabolic profile occur. The present study examined tie effects of acute exposure to ozone on the metabolic properties of hamster heart(H), liver(L), and gastrocnemius(G) tissues. Measures included in vitro oxidative capacity(Q02) and the optimal activity of the marker enzymes 2-oxoglutarate Dehydrogenase(20GDII), Carnitine Palmitoyltransferase(CPT), hexokinase(HI;), Glucose-6-Phosphate Dehydrogenase(G6PDH), and Lactate Dehydrogenase(LDH). Relative to controls, both L and G tissues had significantlydepressed QC02 values(Pc0.01). Heart was unaffected. Significant treatment effects were also found for 20GDH(H,L), CPT(L), HK(H), and G6PDH(H). The data support previous work on lung and erythrocytes suggesting shifts in metabolic profiles in an attempt to counteract the deleterious effects of ozone exposure on cellular lipids or enzymes with sulfhydryl groups. Thepresent data also indicate that brief exposure to ozone will have an effect upon tissues other than the lungs or erythrocytes.

Transparent neural network modelling

Roadknight, C. M. January 2000 (has links)
No description available.

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